I imagine any light dimmer would work ... but here is the one I used and I'd buy the same one again.Click Here (www.doitbest.com)(hey .. list price from the mfg is a lot less than I paid at the hardware store - I've noticed this since moving to California - everything is more expensive)Some have a push/push to turn completely off/on (I wouldn't want that) - this one clicks to OFF when you rotate it just past the slowest setting. There is no reason you would ever want to turn it off unless you wanted to let it sit with no flow at all for preinfuse - which might risk letting the coffee pressure back up into your boiler on machines with a 3-way valve because that valve would remain open with the pump stopped - so I always leave the pump running but at very, very slow setting if I want a long preinfuse. I'll use a higher setting to get the puck saturated and then slow the pump down to let the puck soak if I want that long a preinfuse - but if you want you can simply have a 3bar preinfuse for 10 seconds then 9 bar shot for 10 seconds and then 4 bar end of shot for 7 seconds - or whatever you desire for the particular coffee you are using.

This dimmer had three wires (one was ground) I didn't use the ground wire and just put the dimmer in series with the pump - worked great and was super easy.

Just thought I'd mention ... using a dimmer is not new (many people have done this before). What was new (at least for me) was the idea I got from Jim (Schulman) on the HB site when he was testing out the Bezzera Strega lever/pump hybrid.

Before, I would have done a 3-4 bar preinfuse and then held the shot at 9 bar for the rest of the shot. And for standard espresso roasts that may still be the perfect way to pull them ... but Jim found that he could make great espresso from coffees that would never have worked as espresso before - what he was doing was forgetting about what the pressure actually was and instead he was controlling the pressure while watching the color and rate of flow of the pour. By keeping the espresso flowing really slowly, he felt he was spending more time in the phase of extraction where the chocolate and lower notes develop and was able to get flavors that were more like a french press brew but concentrated and creamy like a ristretto (something you'd never get from a French Press).

And that is what I'm finding too ... I'm able to take "high toned" coffees that would be all citrus peel and tea tasting in a normal espresso pull ... and now I can get a rich, creamy, chocolate shot from that coffee. If you actually watched the pressure it would probably look like a roller coaster where I go up to 9 bars and then drop almost to 2-3 bars for a few seconds and gradually bring it up a bit and the start tapering it off again towards the end of the shot --- but the pour itself looks very even and stays dark longer.

Another thing I ought to mention .... if you try this on a machine without a 3-way solenoid valve, you will get different results. I would expect that the flow would stop coming from the group as you start slowing down the pump. You'd still be able to vary the pressure but the range would probably all be in the upper half of the dimmers rotation and I'd expect you'd stop getting any flow at the slower settings.

I agree with Andy about the effect on the espresso, which is extraordinary. For the SO espresso I have at the moment, I'm doing preinfusion at a really low flow rate, so that the bottom of the basket darkens at about 20s, then pull to 9bar for 5s then drop it back to low flow for another 20s. This gives a rich, creamy shot which still has all that explode-in-the-mouth brightness. I believe this is standard operating procedure on a Slayer. The puzzle for me though is the dimmer (I'm doing this with a couple of needle valves in parallel). I tried a couple of different dimmers, a proportional SSR and ballast resistors with two different Ulka EP5 pumps and none of these was able to maintain a flow of around 60ml/min into around 5bar, which is what you need for this. 60ml/min into 9 bar was fine, as was 90ml/min into 5 bar - but at low flows into medium pressures the pump would behave erratically. So, for those of you in the US I suggest you run out and get precisely the dimmer that Andy uses!

this is pretty much what im trying to do but with some sort of valve after my OPV before my boiler. I need something that will let me manually switch(im thinking electronically) from full flow(9bar) to 5bar.

i started another thread in the mods section about the type of valve i may need. anyone have any idea?

9bar full flow --> hit the switch and drop down to 5psi --> hit the switch again and back to full 9bar

The puzzle for me though is the dimmer (I'm doing this with a couple of needle valves in parallel). I tried a couple of different dimmers, a proportional SSR and ballast resistors with two different Ulka EP5 pumps and none of these was able to maintain a flow of around 60ml/min into around 5bar, which is what you need for this.

I have not tried pulling large volume shots -- I didn't test that at all and it likely wouldn't be able to. I have always pulled ristrettos - 20-30ml in 25-35 seconds is the perfect shot for my tastes. And the vibe pump with dimmer has no trouble putting that flow out .... but, again, I'm not monitoring pressure when I'm actually pulling a shot -- I'm only monitoring how the pour LOOKS. And if it weren't pouring fast enough, I would simply turn the dimmer up until the pour was right. This is what was such a revolutionary idea for me - to forget about what the pressure actually is, just adjust it up and down to get the pour rate the way you want it.

The other revolutionary idea (revolutionary to me anyway) that I got from reading Jim's posts - we have always been taught to grind finer or coarser to get the timing of the shot right. Jim's theory is that any particular coffee has a grind setting that is right to get the best flavor from that coffee - regardless of how fast or slow it pours - the grind should stay the same for that coffee to get the right balance. Once Jim finds the grind that is right to get the flavor balance for that coffee, he then adjusts dose (or tries a different basket) to get the shot timing/volume right. When you combine that idea with the concept of adjusting the pressure during the shot focusing only on the pour (and not what the actual pressure is) it becomes a whole different experience.

This was flow rate, I wasn't talking about large volume shots. I too almost never pull espressos of more than 30g. I meant it wasn't able to maintain a flow rate as low as 30ml/30s, or 60ml/min, into a pressure as low as 5 bar. Higher flows or pressures were fine. 1 ml/s is a tiny flow rate, and the solenoid is hardly moving - I found it could stick if it wasn't getting enough voltage, with catastrophic consequences for my coffee. This is why I'm intrigued - maybe the invensys pump is better. As for what you say about extraction, grind size and flow - yes, absolutely, 100% agree. Choose the grind size to get the extraction you want then the flow rate to get the water through in a sensible time (making sure that you hit 9 bar at some point in the process so that it is actually an espresso you're making and not just strong coffee).

Andy, with your setup I am guessing that as you go through the range the dimmer has available (full power -> min power -> off) that the pump follows along directly. Do you find a pretty good range of adjustability or does the dimmer / pump seem to be pretty touchy and that you only have a small range to work in?

I'm probably thinking too far into this but I'm wondering if there'd be some way of running the dimmer in parallel with the pump, I suppose with another load of some sort (maybe just a big fat resistor). Thinking that might give more range of adjustment. Maybe it's not necessary.

I guess what I'm really wondering, since I'd love to try this myself, is - does it work beautifully or if you did it again would you do it differently?

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